Displays

Displays Category

The various different monitors and the related jargon clarified

Unbalanced Pin

  • Describes concave and convex lines on opposite sides of the screen.

Trapezoidal Distortion

  • A type of geometric distortion where the vertical edges of an image slant inwards towards the top horizontal edge. Also called keystone distortion.

Twisted Nematic – TN

  • The first LCD technology. It twists liquid crystal molecules 90 degrees between polarises. TN displays require bright ambient light and are still used for low-cost applications.

Thin Film Transistor – TFT

  • A type of LCD flat-panel display screen, in which each pixel is controlled by from one to four transistors. TFT technology provides the best resolution of all the current flat-panel techniques. TFT screens are sometimes called active-matrix LCDs.

Tesla

  • Magnetic fields, or more specifically, magnetic flux densities historically have been measured with a unit called the milligauss – 1 milligauss(mg) being equal to 0.001 Gauss(g). Electrical engineers and physicists use the Tesla as a unit of international standard, one Tesla being the equivalent to 10,000 Gauss or 10,000,000 milligauss. Typically the Tesla is used in technical journals and the milligauss unit is used in information for the general public.

Stripe Pitch

  • This is similar to dot pitch, but applicable tubes which the aperture grille method to separate phosphors. Dot stripe is measured as the distance between the vertical stripes that result. Measures of dot pitch and dot stripe are not directly comparable.

Streaking

  • A visual effect which is related to “white level shift” and “black level shift”, where the difference in intensity between neighbouring white and black areas results in a discoloration. Occurs when a CRT’s electron gun does not switch on and off quickly enough.

Slotted Mask

  • A variation on the aperture grill phosphor triad approach which uses the slot-mask design used on many non-Trinitron TV sets.

Shadow Mask

  • The perforated metal sheet that rests between the electron gun and a screen’s phosphor coating to ensure that the three electron beams only strike the correct phosphor dots. A “shadow mask display” is a monitor which conforms to the conventional three-electron gun, shadow mask design.

Screen Regulation

  • A distortion where the size of the image varies according to the brightness of the screen content. A white rectangle will appear larger when surrounding a solid white rectangle than when surrounding a plain black area.

Rotation

  • Determines how well the image area lines up to the bezel; also called tilt.

RGB

  • Red-Green-Blue: a way of encoding images in computer graphics by describing a colour by the amount of the three basic colours Red, Green and Blue. Three bytes are required for “true colour” (three numbers between 0 and 255), giving a theoretical maximum of 16.7 million colours. Computer monitors are generally driven by an RGB signal. The other technique for output display is composite video, which typically offers less resolution than RGB.

Response Time

  • Referring to LCD monitors, this is the time it takes for the liquid crystal inside a screen panel to respond to applied current. Measured in milliseconds, the lower the value, the better the screen can fool the naked eye into seeing fluid movement. Quoted response times may include an element of latency, when a pixel remains lit for a short time after the current has been removed.

Raster

  • A raster is a rectangular grid of picture elements representing graphical data for display. Raster operations (ROPs) can be performed on some portion or all of the raster.

Pixel Clock Speed

  • The frequency or speed at which individual pixels (picture elements) in an image are written to the screen. The higher the pixel clock speed, the less likely there will be flicker.

Pixel

  • An abbreviation for picture element. In a raster grid, the pixel is the smallest unit that can be addressed and given a colour or intensity. The pixel is represented by some number of bits (usually 8, 16 or 24) in the frame buffer, and is illuminated by a collection of phosphor dots in the CRT that are struck by the beams of the electron gun.

Pincushion Distortion

  • The opposite of barrel distortion. The vertical lines in a rectangular image curve inwards, with an increase in the distortion towards the edges of the image.

Phosphor Triad

  • One red, one green and one blue phosphor that composes a pixel.

Phosphor

  • A luminescent substance, used to coat the inside of the cathode-ray tube display, that is illuminated by the electron gun in the pattern of graphical images as the display is scanned.

Plasma Display Panel – PDP

  • A display technology that works on the principle that passing a high voltage through a low-pressure gas creates light.

Passive Matrix

  • A common LCD technology used in laptops. Passive matrix displays (DSTN, CSTN, etc.) are not quite as sharp and do not have as broad a viewing angle as active matrix (TFT) displays, but they have improved dramatically in recent years.

Parallelogram Distortion

  • A type of geometric distortion, where lines are parallel but not perpendicular.

PanelLink

  • Developed by Silicon Images Inc. to provide an all digital link between a graphics card and an LCD monitor, PanelLink uses Transition Minimised Differential Signalling (TMDS) signalling technology, allowing a distance of up to 10m between the graphics card and the LCD panel.

Overscan

  • A condition that exists when a created image is larger than the visible portion of the display. Overscan helps relegate the relatively fuzzy perimeter of a CRT image to portions of the screen that are out of sight, and the overscan may disappear over time anyway. On the other hand, monitors with excessive overscan can lose icons and text at the edges of the display.

OLED

  • Organic Light-Emitting Diode: a display device invented by Eastman Kodak in the early 1980s. OLEDs sandwich carbon-based films between two charged electrodes, one a metallic cathode and one a transparent anode. The organic films consist of a hole-injection layer, a hole-transport layer, an emissive layer and an electron-transport layer. When voltage is applied to the OLED cell, the injected positive and negative charges recombine in the emissive layer and create electro luminescent light.

nT

  • nano Tesla: a unit of measurement for magnetic flux density. A magnetic field of one Tesla is very strong – the earth’s magnetic field is only tens of nano-Teslas.

nit

  • A unit of luminance equal to one candlepower measured at a distance of 1m over an area of 1 square metre. One nit is equal to 1 candela per square metre or 0.2919 fL (footlamberts).

Multiscan

  • A monitor that can display many different resolutions. A single-scan monitor can only display a particular resolution.

Multi-Frequency

  • A monitor’s ability to change resolution or refresh rate when signalled by a video adapter. Graphics adapters have the ability to “tell” a monitor to use various display resolutions and refresh rates. If the resolution or refresh rate is within a monitor’s scanning range, multi-frequency monitors adjust to the resolutions and refresh rates “ordered” by the video adapter. Also known as multi-scanning. See also Modes.

MPR2

  • Provides reduced electrostatic and electromagnetic emissions. MPR 1990, or MPR2, is a standard defined to measure emissions from devices such as monitors.

Modes

  • Specific frequencies at which the monitor (and/or computer) can display text or graphical information. Most monitors today support several frequencies. This is called multifrequency or multi-scanning, and it ensures that the monitor will perform with a variety of computers and applications.

LEP

  • Light-Emitting Polymer: a display technology in which plastics are made to conduct electricity and, under certain conditions, emit light.

LED

  • Light Emitting Diode: a display technology that uses a semiconductor diode that emits light when charged. LEDs are usually red. It was the first digital watch display, but was superseded by LCD, which uses less power.

Liquid Crystal Display – LCD

  • A display technology that relies on polarising filters and liquid crystal cells rather than phosphors illuminated by electron beams to produce an on-screen image.

Jitter

  • The interference that occurs – causing a shimmering effect that results in lines and characters to losing their focus – when a TFT panel’s clock and phase aren’t perfectly synchronised.

Invar

  • Type of metal used in the shadow mask that provides more consistent images over time, by reducing warping of the shadow mask when bright images are displayed.

Interlaced

  • Scheme to display a video image by displaying alternate scan lines in two discrete fields.

HSF

  • Horizontal Scanning Frequency: indicates the speed, measured in kilohertz, at which a single horizontal line is drawn on the screen. Higher scan rates are needed to provide sharper, crisper images at higher resolutions. Also called scan rate.

Ghosting

  • A visual effect in which an area of “on” pixels causes a shadow on “off” pixels in the same rows and columns. A particular problem with passive matrix LCDs.

FST

  • Flat Square Tube: describes the viewing surface of a cathode ray tube that is nearly flat. Flatter screens give the appearance of straighter lines, and they can aid in the reduction of glare, compared to conventional tubes.

Footlambert

  • fL: a unit of luminance equal to 3.463 candelas per square metre.

Flat Panel Display

  • A thin display screen that uses any of a number of technologies, such as LCD, plasma and FED. Traditionally used in laptops, flat panel displays are slowly beginning to replace desktop CRTs for specialised applications.

FED

  • Field Emission Display: a display technology which use vacuum tubes (one for each pixel) with conventional RGB phosphors.

Energy Star

  • Launched in 1993, this is a program established by the Environmental Protection Agency (EPA) as a partnership with the computer industry to promote the introduction of energy-efficient personal computers which help reduce air pollution caused by power generation. To comply with the Energy Star guidelines, a computer system or monitor must consume less than 30 watts of power in its lowest power state.

Electron Beam

  • The invisible stream of electrons that flow from a CRT monitor’s cathode to its screen.

EDP

  • Enhanced Dot Pitch: Hitachi’s tube technology in which the phosphor triads are spaced closer together horizontally than they are vertically.

Dynamic Focus

  • The ability of a CRT monitor’s electron gun to adjust focus so that it is sharp across the whole screen – not just the centre.

Double-layer SuperTwist Nematic – DSTN

  • A passive-matrix LCD technology that uses two display layers to counteract the colour shifting that occurs with conventional supertwist displays. Also referred to as dual-scan LCD.

DPMS

  • Display Power Management Signalling: displays or monitors that comply with this can be managed by Power Management features found in CMOS configuration on Energy Saving PCs.

Dot Trio

  • The standard phosphor triad arrangement.

Dot Pitch

  • A measurement of distance between the centres of two same-colour phosphor dots on the screen. The closer the dots, the smaller the dot pitch, and the sharper the image. See also Stripe Pitch.

DMD

  • Digital Micromirror Device: an array of semiconductor-based digital mirrors that precisely reflect a light source for projection display and hard-copy applications. A DMD enables Digital Light Processing and displays images digitally. Rather than displaying digital broadcast signals as analogue signals, a DMD directs the digital signal directly to your screen.

DLP

  • Digital Light Processor: an all-digital display technology that turns image data into light. Enabled by a DMD device, DLP is capable of projecting sharp, clear images of almost any size without losing any of the original image’s resolution.

Deflection Yoke

  • The arrangement of electromagnets which can alter the direction of the electron beam that passes through it.

Degauss

  • Magnetic interference caused by a change in the position of a monitor in relation to the earth’s magnetic field or the presence of an artificial magnetic field can cause discoloration. To correct this, all colour monitors automatically degauss at power-on and some also have a manual degaussing button. This allows the monitor to compensate for the change in the magnetic field by realigning the electron guns.

DDC

  • Display Data Channel: DDC 1/2B and 2AB are standardised techniques by which monitors and graphics cards communicate with each other to help establish the best resolution and refresh rate combination. DDC is only possible through a D-SUB connection.

D-SUB Connector

  • A type of monitor socket and cable plug found on all PC monitors. It consists of a single cable that carries all the video information and uses the same pin layout as the socket on a graphics card.

CSTN

  • Colour Super-Twist Nematic: a passive matrix LCD technology developed by Sharp Electronics Corporation.

Cathode Ray Tube – CRT

  • The tube of a television or monitor in which rays of electrons are beamed onto a phosphorescent screen to produce images. Often used as a generic term for a computer monitor.

Convergence

  • The term used to describe how accurately the three (red, green, and blue) electron beams converge to illuminate their respective phosphors in a colour monitor. The better the guns converge, the sharper the image. If a monitor shows poor convergence, edges of objects will have a red, blue or green tinge.

Composite Video

  • A video signal format that includes the complete visual waveform, including: chrominance (colour), luminance (brightness), blanking pedestal, field, line, colour sync pulses and field qualising pulses.

Colour Temperature

  • Defines the whiteness of the white on the screen. Variations are measured in degrees Kelvin. Natural colours used in life-like images, such as people or landscapes, look more true to life when displayed at a colour temperature of 6500K. Black text on a white page is better represented by a colour temperature of 9300K.

Cathode

  • An electrode that is negatively charged. Electrons are released from the cathode in a CRT monitor.

Candela

  • A unit of measurement of the intensity of light. An ordinary wax candle generates one candela. The maximum brightness for CRTs is about 100 to 120 cd/m2 and for TFTs, up to 250 cd/m2.

BNC

  • A video connection type found on many high-end monitors. It consists of five separate cables for red, green, blue, horizontal and vertical synchronisation signals.

Blooming

  • A problem where bright white areas have a slight halo around them.

Bifringence

  • The property of a material which causes incident light waves of different polarisations to be refracted differently by the material.

Bezel

  • The border around the edge of the screen, covering the extremities of a CRT. Also used to describe the rim around the perimeter of faceplates – often clip-on – of drive bays and even PC cases, used to vary their appearance.

Barrel Distortion

  • A type of image distortion where vertical lines are bowed outwards, towards the edges of the screen.

Backlight

  • An LCD screen that has its own light source from the back of the screen, making the background brighter and characters appear sharper.

Autoscan

  • A microprocessor-based feature of some monitors incorporating automatic synchronisation of their horizontal and vertical frequencies with those of the installed video graphics adapter. An autoscan monitor can thus operate with a wide range of video adapters.

Astigmatism

  • A lens aberration that causes off-axis light electron beams to focus to an elliptical, rather than circular, spot. The larger the monitor size, the greater the problem.

Aspect Ratio

  • The relationship of width and height. When an image is displayed on different screens, the aspect ratio must be kept the same to avoid “stretching” in either the vertical or horizontal direction. For most current monitors, this ratio is 4:3. For HDTV, the ratio is generally 16:9.

Aperture Grille

  • The phosphor separation method used in a Trinitron CRT in place of a shadow mask. A series of thin, closely-spaced vertical wires are used to isolate pixels horizontally. The pixels are separated vertically by the nature of the scan lines used to compose the image.

Anode

  • A positively charged electrode used to attract (negatively charged) electrons in a CRT monitor.

Ambient Light Sensor

  • A light sensor at the top of the monitor which gauges ambient light in the work environment and automatically adjusts the brightness of the monitor for optimum viewing. This takes away the frequent and tedious task of manually adjusting brightness on the screen; it is particularly beneficial in environments where light in the office is subject to change throughout the day.

Additive Colour

  • Colour produced by “adding” colours, usually the combination of red, green and blue.

Active Matrix

  • An LCD technology used in flat panel computer displays. It produces a brighter and sharper display with a broader viewing angle than passive matrix screens. Active matrix technology uses a thin film transistor at each pixel and is often designated as a “TFT” screen. See also Passive Matrix.

HTPS

  • High Temperature Poly-Silicon: A thin-film transistor (TFT) panel is an active matrix display containing a microscopic thin-film transistor in the corner of each pixel. HTPS panels allow driver ICs to be embedded into their TFTs, thereby allowing greater miniaturisation (higher pixel counts and higher aperture ratios).

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